Prism proposed for UK plutonium disposal

01 December 2011

GE-Hitachi Nuclear Energy (GEH) has proposed the construction of a nuclear power plant comprising two Prism fast reactors at Sellafield to assist the UK in disposing of its of reactor-grade plutonium stockpile.

A two-module Prism plant (Image: GEH)

The proposal comes as the UK government consults on ways to manage its stockpile of uranium. The country is currently storing about 112 tonnes of civil separated plutonium at Sellafield, including some 28 tonnes of material belonging to overseas customers. The plutonium stored in the UK has been derived largely from nuclear fuel reprocessing activities that have been ongoing at Sellafield since the 1950s.

GEH has now suggested to the UK government that a plant comprising two 311 MWe Prism (Power Reactor Innovative Small Module) units should be built at Sellafield. The pool-type modules, built below ground level, contain the complete primary system with sodium coolant. These units would irradiate fuel made from the plutonium stored at the site. This fuel would consist of a mix of metal plutonium and depleted uranium. After 45-90 days of irradiation, GEH said that the fuel would be brought up to 'spent fuel standard' of radioactivity, after which is could be stored in air-cooled silos. It would then be suitable for disposal alongside the UK’s other high-level forms of radioactive waste.

According to GEH, the UK's entire plutonium stockpile could be irradiated in such a plant within five years, during which time the plant could also generate some electricity. Once all the stockpile of plutonium has been irradiated, the Prism plant could then start re-using the fuel solely for electricity generation. Fuel stays in the Prism reactor for about six years, with one-third removed every two years. The plant could operate for up to 60 years. Although used Prism fuel can be recycled after removal of fission products, GEH's proposal does not include a reprocessing plant at Sellafield, although one could be added later.

Opposite direction

Separately the UK government has confirmed its 'preferred policy' for plutonium disposal to be a new mixed-oxide (MOX) fuel manufacturing plant:

"While the UK government believes it has sufficient information to set out a direction, it is not yet sufficient to make a specific decision to proceed with procuring a new MOX plant."

"Only when the government is confident that its preferred option could be implemented safely and securely, that is affordable, deliverable, and offers value for money, will it be in a position to proceed with a new MOX plant."

"If we cannot establish a means of implementation that satisfies these conditions then the way forward may need to be revised."

GEH anticipates the cost of the Sellafield plant would be comparable to that of a large conventional reactor. The company said that it has started to develop a supply chain in the UK to support its proposal.

General Electric (GE), together with the US national laboratories, had been developing Prism under the Advanced Liquid Metal Reactor/Integral Fast Reactor (ALMR/IFR) program funded by the US Department of Energy (DoE). That program was cancelled in 1994, but not before a pre-application safety evaluation report for the original Prism design concluded that "no obvious impediments to licensing the Prism design had been identified."

GEH - a joint venture between GE and Japan's Hitachi - is now touting the Prism design as its Generation-IV solution to closing the nuclear fuel cycle in the USA.

In October 2010, GEH and Savannah River Nuclear Solutions - a partnership between Fluor, Northrop Grumman and Honeywell - signed a memorandum of understanding to consider constructing a prototype Prism reactor at the DoE's Savannah River site in South Carolina. It would be built as part of a proposed demonstration of small reactor technologies.